Just scratching the surface (not including Magento or WooCommerce) take a look at some of open source solution which can be installed on bare-metal, cloud or used as SaaS offered by providers. These all are ready to deploy solution in hours and days (obviously as stated earlier the difficult part is not this but the business itself. ):
1. Spree [1] Store Demo [2]
2. Saleor [3] Store Demo [4]
3. Reaction [5]
4. Solidus [6]
5. Medusa [7]
6. Sylius [8]
7. Shuup [9]
8. Vendure [10] Demo Store [11]
9. Shopware [12]
10. Vue-Storefront [13] - works with many of the above backend.
11. nopCommerce [14]
12. Bagisto [15]
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Links:
[1] https://spreecommerce.org/spree-as-a-service/
[2] https://spree.vercel.store/
[4] https://saleor.vercel.store/
[5] https://mailchimp.com/developer/open-commerce/
[11] https://vendure.vercel.store/
[12] https://www.shopware.com/en/
[13] https://www.vuestorefront.io/cloud
[14] https://www.nopcommerce.com/en/enterprise-ecommerce-platform